What is MTHFR?
By Russell Browne (Dip. Adv. Nut.) · Specialist in Genetic Nutrition & Methylation Protocols
MTHFR is one of the most-searched genes in health — and one of the most over-hyped. This page gives you the clear, honest version: what the MTHFR gene does, what its common variants really mean for folate and homocysteine, what the research supports, and how to find your own result. It’s also the starting point that links out to our detailed MTHFR guides.
What is MTHFR?
MTHFR is short for methylenetetrahydrofolate reductase — both a gene and the enzyme it makes. That enzyme helps convert folate (vitamin B9) from your diet and supplements into its active form, 5-MTHF (“methylfolate”), which your body uses for methylation, DNA production, and keeping the amino acid homocysteine in balance. In short, MTHFR is a key step in how your body puts folate to work.
What is an MTHFR “mutation”?
The MTHFR changes people search for as “mutations” are, for the most part, common polymorphisms (variants) — not rare defects. The two most studied are C677T (rs1801133) and A1298C (rs1801131). You can carry no copies, one copy (heterozygous), or two copies (homozygous) of each, inheriting one from each parent. Carrying an MTHFR variant is common and widespread — a large share of the population has at least one — and on its own it is not a diagnosis.
What folate does (and folate vs folic acid)
Folate (vitamin B9) supports several essential jobs: making and repairing DNA, single-carbon metabolism (methylation), producing and maturing blood cells, helping make neurotransmitters, and processing homocysteine. For these to run smoothly, the body converts folate into active 5-MTHF with the help of several nutrient co-factors — and MTHFR is one important part of that conversion.
It’s worth knowing that folate and folic acid are not the same: folate is the natural form, while folic acid is synthetic and must be converted before the body can use it. This distinction comes up often in MTHFR discussions.
New to all this? Start with the overview
Bad Genes – The Genetic Advantage by Russell Browne is a plain-English tour of the common gene variants that most influence health — the ideal companion to your variant report, and a great place to see how the individual genes fit together.
MTHFR variants: what the research shows, and what we see in practice
There is a great deal written about MTHFR online, and much of it overstates the case — tying a common variant to long lists of serious diseases. We want to be more careful and more useful than that, so we separate two kinds of information.
What the research shows
MTHFR variants (particularly two copies of C677T) have been associated with modestly reduced enzyme efficiency and, in some people, higher average homocysteine — an effect strongly influenced by folate status. Researchers have also studied MTHFR in relation to specific outcomes in particular populations. Reference.
Three points are essential to keep in view:
- MTHFR variants are common — carrying one is normal and widespread.
- The findings are associations — relative shifts in likelihood — not causation. A variant does not, by itself, cause disease.
- Many people with MTHFR variants are perfectly healthy. Homocysteine and health depend on far more than this one gene — folate and B12 status, other genes, and lifestyle all matter.
One important distinction: the common MTHFR variants on a consumer report are not the same as homocystinuria, a rare, serious inherited disorder caused by different, uncommon mutations and diagnosed clinically. Confusing the two is a common source of unnecessary worry.
What we observe in clinical practice
Drawing on years of nutritional practice, we consider MTHFR as one part of a wider methylation and folate picture — alongside actual bloodwork, symptoms, and the other genes involved — rather than treating a single variant as the whole story. These are clinical observations, considered case by case. They are not a diagnosis, and a genotype is not a supplement protocol. Anything you wish to act on is best assessed individually with a qualified practitioner.
MTHFR and homocysteine
Because active folate helps recycle homocysteine, reduced MTHFR efficiency can be one factor in higher homocysteine for some people — but the gene does not set your level. Homocysteine is influenced by folate, B12 and B6 status, other conditions, and more, which is why it is measured with a blood test rather than predicted from DNA. For the full picture, see our detailed guide: MTHFR and Homocysteine: What the Research Shows.
Want to go deeper on homocysteine?
Homocysteine – The Genetic Advantage by Russell Browne is a plain-English guide to what homocysteine is, how the methylation genes influence it, and why a blood test tells you more than a gene alone — the ideal companion to your variant report.
Explore MTHFR in more detail
This page is the overview. For specifics, see our plain-English guides:
- MTHFR C677T explained
- MTHFR A1298C explained
- How to find your MTHFR result in 23andMe data
- MTHFR and homocysteine
- The methylation genes in your raw data: a map
How to find your MTHFR result
Your existing 23andMe, AncestryDNA, or MyHeritage raw data file already contains your MTHFR markers — you do not need a new test. Upload it to our genetic app to generate a plain-language variant report showing your MTHFR result (and many others), which you can then review with a practitioner in the context of your whole health picture.
Order or view your report · Find a practitioner
Important note
This page is educational and is not a diagnosis or a treatment plan. MTHFR variants are common and shift relative likelihood, not certainty; many people who carry them are healthy. The clinical observations reflect what we have seen in practice and will not apply to everyone. Anything you wish to act on should be assessed individually with a qualified practitioner who can consider your full history, symptoms, and any relevant testing.
About the Author
Russell Browne (Dip. Adv. Nut.)
Specialist in Genetic Nutrition & Methylation Protocols
Russell Browne is a qualified practitioner of Advanced Nutrition, Advanced Herbalism, and Homeopathy, with a specialized clinical focus on genetic nutrition, methylation pathways, and detoxification. With years of dedicated clinical experience helping patients decode complex chronic health issues, Russell is also the author of How to Treat Your MTHFR Gene Mutations the Right Way – The Genetic Advantage and several works on genetic wellness. He is committed to bridging the gap between complex genetic data and practical, root-cause clinical care.
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